pgsql: amcheck: Report an error when the next page to a leaf is not a l

amcheck: Report an error when the next page to a leaf is not a leaf

This is a very unlikely condition during checking a B-tree unique constraint,
meaning that the index structure is violated badly, and we shouldn't continue
checking to avoid endless loops, etc.  So it's worth immediately throwing an
error.

Reported-by: Peter Geoghegan
Discussion: https://postgr.es/m/CAH2-Wzk%2B2116uOXdOViA27SHcr31WKPgmjsxXLBs_aTxAeThzg%40mail.gmail.com
Author: Pavel Borisov

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/97e5b0026fc276ab1bcde58ae98ae1fcd9c3acc3

Modified Files
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contrib/amcheck/verify_nbtree.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)